Cascaded triode-pentode counter circuit



March 11, 195 w. J. ANDERSON CASCADED TRIODE-PENTODE COUNTER CIRCUIT Filed Aug. 30, 1955 INVENTOR ATTORNEY United States Patent @tiic 2,326,688 Fatentecl Mar. 11, 1958 CASCADE!) TRIODE-PENTODE COUNTER CIRCUIT Walter J. Anderson, Chicago, Ill., assignor, by mesne assignments, to Chicago Musical Instrument Company, Chicago, 111., a corporation of Illinois Application August 30, 1955, Serial No. 531,496

1 Claim. (Cl. 250-27) My invention relates broadly to electron tube circuits and more particularly to cascaded triode-pentode counter tube circuits.

One of the objects of my invention is to provide a triodepentode tube circuit for counting tube units in which the plate, grid, and cathode, of the triode serve as one-half of the counting tube unit and the cathode, control grid, and screen grid of the pentode serve as the other half of the counting tube unit.

Another object of my invention is to provide a circuit arrangement for a composite triode-pentode counting tube in which the plate of the pentode is a free element which may be used as a signal removing element which within limits operates independently of an associated flip-flop circuit.

A further object of my invention is to provide a counting tube including a composite triode section and pentode section in which certain of the respective tube elements are electronically coupled within the envelope of the tube and wherein the signal voltage may be taken oif from the tube without loading any of the elements in the tube which are being used for counting purposes.

A still further object of my invention is to provide a composite triode-pentode tube circuit wherein the pentode plate is activated only during those periods that a circuit is closed through a positive potential source and resistive path to the pentode plate independently of the operation of the triode and pentode sections of the tube.

Other and further objects of my invention reside in the coactive relationship of triode and pentode groups of electrodes in the same enclosing envelope and associated external circuits as set forth more fully in the specification hereinafter following by reference to the accompanying drawing which diagrammatically illustrates the composite triode-pentode tube system as applied to the keying circuit of an electronic organ.

The art of multi-vibrator circuit operation and Eccles- Jordan circuit operation has long employed the use oi dual triodes per stage as well as operating with separate pentodes two per stage. The plates of such tubes have been used as an integral part of the flip-flop circuit. One of the attending weaknesses of such prior systems is that when taking a useful signal from one of the flip-flop elements, it is required that a very high impedance output circuit be used so as not to load down the flip-flop circuit. If the flip-flop circuit is loaded down excessively, it becomes unstable and the operation becomes unreliable. My invention pertains to the use of a triode-pentode as a counter tube with the plate grid and cathode of the triode serving as one-half of the counting unit and the cathode control grid and screen grid of the pentode serving as the other half of the counting element. Thus, the plate of the pentode is a free element which may be used as a signal removing element which within limits operates independently of the flip-flop circuit. Thus, regardless of how great a load is placed upon the plate, the flip-flop section of the tube continues to operate regardless of such load. By use of the system of my invention greater stability, dependability, reliability and uniformity of operation is assured and synchronous operation of cascaded generators and followers is obtained with high efficiency.

Referring to the drawing in detail, reference character 1 designates the first follower of a cascaded generator consisting of two groups of electrodes enclosed in the same envelope, one group of electrodes constituting a triode and the associated group of electrodes comprising a pentode. A second follower is designated at 2 similar in all respects to the first follower 1. The groups of electrodes in the follower 1 constituting the triode consists of the cathode 1a, the control grid 11), and the plate is. The group of electrodes constituting the pentode comprises the cathode la', the control grid 1b, the screen grid 1d, the suppressor grid 12, and the plate 10'. The groups of electrodes in the second follower 2 correspond to the groups of electrodes in the first follower 1 and have been indicated by reference characters 2a, 2b, and 20 consisting of cathode, control grid, and plate of the triode section and 2a, 212, 2d, 2e, and 2c constituting the cathode, control grid, screen grid, shield grid, and plate of the pentode section.

The synchronizing signal from a master pulse generator (not shown), is applied to the first follower 1 from the input terminal 3 and ground connection 4 from any suitable driving source such as a Hartley oscillator. The input signal is applied to the junction point 5 between resistors 6 and 7 through the condenser 8 and transmitted to the control grids 1b and 1b through condensers 9 and 10. The plate is of the triode section of the first follower 1 and the screen grid 1d of the pentode section of said follower 1 in turn flop and the counter-action follows according to a flip-flop operation. The plate 10 of the pentode section of follower l is electronically coupled to the cathode in, control grid 1b, and screen grid 1d of the pentode section by Way of electrons within the tube. Thus a flip-flop signal appearing within the elements of the pentode is also seen at the plate 10' which is connected to a source of positive voltage through resistor 11 and a key switch 12 from ground connection 14 through resistor 15 and condenser 16. When the key switch 12 is in the on position illustrated in dotted lines, the signal energy is applied to the key switch collector bus indicated at 17. in a similar manner a synchronizing signal is transmitted from the plate 1c of the triode section of the follower 1 through condenser 18 to the junction point 19 of resistors 29 and 21 of the second follower or counter 2, and similarly to any number of counters in cascade.

The circuit of the follower 1 is completed by resistor 21 which is shunted between control grid 1b of the triode section and screen grid 1d of the pentode section. The bias on the suppressor grid 1e and control grids 1b and 1b is controlled by cathode resistor 22 and associated shunting condenser 23. The input circuit to the control grid 1b and cathode 1a of the triode section of the follower 1 is completed through the resistor 24. The positive potential supplied to the plate 10 of the triode and the potential supplied to the screen grid of the pentode is controlled by resistor 25. The input circuit to the pentode section of the follower 1 is completed through resistor 26. The output circuit of follower 1 is completed by resistor 27 which connects between control grid 1b of the pentode section and the plate 10 of the triode section in shunt with condenser lit.

The circuit of the cascaded follower tube 2 is similar in all respects to the circuit of follower tube 1 and in order to emphasize the corresponding circuit elements I have indicated the corresponding circuit elements by the same reference characters, with the prime designation added at 11', 12', 14', 15, 16', 10', 18, 22', 23, 26', and 27'. Each of the follower tubes operates in a similar manner and the take-off signal is derived from each tube without loading any of the elements in the tubes which are being used for counting purposes. The pentode plates 1c and 2c are only activated when the positive potential is applied thereto. Signal therefrom is removed through the associated key and resistor shown at 12 and 15.

I have found the combination triode-pentode counter system as set forth herein stable and reliable in operation, with the plates of the pentodes operating free and independently of the operation of the flip-flop circuit embodiments. I realize that modifications may be made and I desire that it be understood that no limitations upon my invention are intended other than may be imposed by the scope of the appended claim.

What I claim and desire to secure by Letters Patent of the United States is:

In an electrical musical instrument employing playingkeys, a counter circuit comprising a plurality of vacuum tube stages coupled in cascade and respectively producing audio tone signals at octave separation, each of said stages consisting of a triode'section and a pentode section in which all electrodes of both sections of each stage except the plates in the pentode sections of said stages are connected in circuit for operation of said stages at octave separation; a playing-key operated switch for each said stage for withdrawing signal voltage from said stage via the plate in the pentode section thereof, the plate of the pentode section of each stage being free of any circuit connection with other electrodes of either section of said stages other than by the electron stream when said stages are activated so as to enable withdrawing signal voltage from any one or more of said stages and prevent overloading said stages and thereby maintain the aforementioned octave separation of signal voltages produced by said stages, the plate of the pentode section of each of said stages being connected to a source of positive potential through a resistor; a path for and connecting each separate key-operated switch to the place of the pentode section of a respective stage; and an output bus bar :connected in common to the respective playing-key operated switches.

References Cited in the file of this patent UNITED STATES PATENTS Larsen July 2, 1946 2,536,917 Dickinson Jan. 2,1951 2,697,781 Trousdale Dec. 21, 1954 

